1. Technical Field
The invention relates generally to interconnect structures, and more particularly, to a composite interconnect structure formed using injected molded solder.
2. Background Art
Composite interconnect structures for coupling a semiconductor device to a substrate are advantageous for a number of reasons. For example, Japanese Patent Publication 7066209A discloses a composite interconnect structure including solder (e.g., gold-tin) with a core of a higher melting point than solder. The composite interconnect structure allows mounting of an optical device on a circuit board without tilting the devices, i.e., the core prevents a bump from compressing more than other bumps during mounting. This reference, however, uses a very difficult process in which the composite interconnect structure is formed by cutting the material into bumps. In addition, this particular interconnect structure does not achieve all of the possible advantages of composite interconnect structures.
FIG. 1 shows one part of a conventional injection molded solder process for forming interconnects. In this process, a molten solder injector 2 is moved across a mold 4 including a plurality of openings 6, injecting the openings with molten solder 8. Mold 4 is then allowed to cool and is positioned over a wafer including one or more semiconductor devices (not shown) and heated to re-flow hardened solder 10 to wettable pads (not shown) on the semiconductor devices. Each semiconductor device (not shown) is then positioned over a substrate and reflowed such that solder 10 forms an interconnection between the semiconductor device and substrate. This technique, however, is incapable of forming composite interconnect structures.
There is a need in the art for a way to provide a composite interconnect structure that does not suffer from the problems of the related art.